1. Field of the invention
The present invention relates to a photo printer, and more particularly, to a photo printer with an adjustable thermal print head for adjusting the contacting stress between the thermal print head and platen roller during photo printings.
2. Description of the prior art
To print high quality photos, the thermal print head and platen roller within the photo printer must be properly adjusted and in even contact with each other. Therefore, precise assembly technique is essential.
Please refer to FIG. 1 and FIG. 1A. FIG. 1 is a schematic diagram of a prior art photo printer 10, FIG. 1A is a perspective view of the photo printer 10. The photo printer 10 comprises a housing 11, a cantilever mechanism 12 rotatably mounted on the housing 11, a thermal print head 14 installed at one end of the cantilever mechanism 12 for printing a photo 38 by heating a ribbon 16, a platen roller 20 rotatably installed in the housing 11 under the thermal print head 14 for carrying the photo 18 forward and backward through the thermal print head 14, a driving mechanism 22 for rotating the cantilever mechanism 12 to drive the thermal print head 14 downward to print the photo when the photo is carried forward by the platen roller or upward when the photo is carried backward by the platen roller, and an elastic strip 24 installed in the housing 11 located at the bottom end of the platen roller 20. When the thermal print head moves downward a fixed distance, it generates a pressure that distorts the elastic strip 24 which then generates a fixed contacting stress between the thermal print head 14 and the platen roller 20.
Please refer to FIG. 2 and FIG. 2A. FIG. 2 is a schematic diagram of another prior art photo printer 30, FIG. 2A is a perspective view of the photo printer 30. The photo printer 30 comprises a housing 31, a shaft 44 installed on the housing 31, a cantilever mechanism 32 rotatably mounted on the shaft 44, a thermal print head 34 installed at one end of the cantilever mechanism 32 for printing a photo 38 by heating a ribbon 36, a platen roller 40 rotatably installed in the housing 31 under the thermal print head 34 for carrying the photo 38 forward and backward through the thermal print head 34, an elastic arm 46 rotatably mounted on the shaft 44 and located at the upper end of the cantilever mechanism 32, an elastic strip 48 installed between the cantilever mechanism 32 and the elastic arm 46, and a wheel 50 installed at the upper end of the elastic arm 46. During printing, the wheel 50 moves downward a fixed distance generating a fixed amount of pressure on the elastic arm 46 and the cantilever mechanism 32 which generates a fixed amount of contacting stress between the thermal print head 34 and the platen roller 40.
Precise assembly and adjustment procedures are necessary to ensure the thermal print heads 14, 34 and the platen rollers 20, 40 are in even contact. This is time-consuming and costly.